An alkylene oxide addition product as obtained by causing an alkylene oxide to add to a hydroxyl-group-containing compound (e.g. alcohols) is, for example, useful for obtaining a polycarboxylic acid which is suitable for a high-performance AE water-reducing agent, wherein the polycarboxylic acid is obtained by carrying out an esterification reaction between the alkylene oxide addition product and an unsaturated carboxylic acid (e.g. (meth)acrylic acid) or a transesterification reaction between the alkylene oxide addition product and an alkyl ester of (meth)acrylic acid, thereby introducing an unsaturated group into the alkylene oxide addition product, and thereafter carrying out copolymerization of the resultant product with an unsaturated carboxylic acid. The alkylene oxide addition product has hitherto been widely used as a raw material for polymers that are used for uses such as cement additives. In such a case, it is well known to be preferable for further enhancing the performances such as dispersibility that the alkylene oxide addition product has a large molecular weight.
A favorable method for producing the alkylene oxide addition product having a large molecular weight is to cause a larger amount of alkylene oxide to add to the hydroxyl-group-containing compound. However, in this case, the volume of the resultant product is very much larger than the volume of the raw materials as charged. Therefore, it has been usually necessary to use a reactor having a special shape or to use a special stirring apparatus, so there have been various limitations on usable production facilities.
In addition, as another problem occurring when the alkylene oxide addition product is produced by causing the alkylene oxide to add to the hydroxyl-group-containing compound, there has been also a problem such that: when the amount of water existing in the system is large in this addition reaction, by-products (e.g. poly(alkylene oxide)) increases. That is to say, it can also be conceived to use ordinary facilities with the volume of the raw materials as charged being decreased in consideration of the volume of the product. However, when the volume of the raw materials as charged is small, the amount of water mingling from an apparatus is so large relative to the amount of the raw materials as to bring about an increase of the by-products.
Furthermore, if the by-products (e.g. poly(alkylene oxide)) increases as mentioned above, there has been a problem of having an bad influence such that the reaction yield and the reaction selectivity decreases when various reactions are carried out by using the alkylene oxide addition product, particularly, when a (meth)acrylate ester is produced by carrying out an esterification reaction between the alkylene oxide addition product and (meth)acrylic acid or a transesterification reaction between the alkylene oxide addition product and an alkyl ester of (meth)acrylic acid, or when a (meth)acrylic copolymer is produced by carrying out a polymerization reaction of a monomer component including a (meth)acrylate ester as obtained by carrying out an esterification reaction between the alkylene oxide addition product and (meth)acrylic acid or a transesterification reaction between the alkylene oxide addition product and an alkyl ester of (meth)acrylic acid. In a specific explanation for the problem, a (meth)acrylate diester is by-produced when the esterification reaction or the transesterification reaction is carried out, and this (meth)acrylate diester acts as a crosslinking agent when the polymerization reaction is carried out, so that a high-molecular crosslinked polymer is by-produced.
As a production process for the alkylene oxide addition product used as a raw material for polymers that are used for uses such as cement additives, for example, JP-A-220440/2001 discloses a production process in which the water content of a liquid containing a catalyst and an alcohol is suppressed to not higher than a specific value, and JP-A-344883/2000 discloses a production process in which the water content of a reaction vessel is suppressed to not higher than a specific value by drying the reaction vessel after washing it with a solvent, and JP-A-236859/1998 discloses a production process in which an alkylene oxide addition reaction is carried out under specific temperature conditions. However, it is the present state of affairs that there has not yet been solved the problem such that: in the case where the alkylene oxide addition product having a high molecular weight is produced, the volume of the resultant product is very much larger than the volume of the raw materials as charged, therefore it is necessary to use a reactor having a special shape or to use a special stirring apparatus.